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351w piston above deck! help!!
I'm building my first engine and think i've bought the wrong piston. I have 69 351w with trw l-2446f pistons installed. The piston is a flat top with 16cc cup. The piston at tdc is above deck .015. My question is with the head gasket installed will their be enough clearance between the block and the cylinder head?
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'69 block has a lower deck height than all other years of 351W. If you did not specify this when you ordered the parts, you indeed have the wrong parts.
Pete |
Flip,
What kind of rods are you using? LH |
Sorry Flipper
According to the specs for the TRW-L2446f pumps, they are for 9.503 deck height blocks. The '69 is 9.482 or something like that. You MIGHT be able to put a GOOD head gasket on and get by, (not all would work!) Being your first build, you should check into swapping out the TRW's for something else or playing with the rod length as Harris is implying....good luck!
greg Specifications: * Bore: 4.00 in. * Stroke: 3.50 in. * Rod length: 5.956 in. * Compression ratio: 9.19:1 (60.4cc heads), 8.95:1 (63cc heads), 8.46:1 (69cc heads) * Head type: .110 in. dish * Oversize: Standard * Ring size: 5/64 in. top/second ring, 3/16 in. oil control ring * Weight: 639 grams * Pressed pin only * 351W block with 9.503 in. deck height |
I hate bad news! Everything was going great until this. Do you think the piston tops can be skinned. I have the tfs heads with 61cc so the compression was going to be low. I think if the piston is skinned the cup would be reduced thus increasing compression. Right? Compression under 10:1 would be okay. What do you guys think? Thanks for your help.. Terry
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my opinion...
you're into this project how many thousands? just buy the right set of pistons and chalk it up to experience. maybe save these for your next (taller deck) block. want to hear about my headers that fit FORD heads, but don't match up to Edelbrocks? |
You have the wrong pistons. Best to trade them in and get the right ones for a '69 block. Otherwise you can probably have someone skim the .015 off the top and maybe get by OK if the top doesn't get too thin. You'll also have to double check valve reliefs. Compression will probably go lower because the volume of the cylinder is larger per .001" than the relief cut into them. I wouldn't try to compensate for wrong pistons by juggling head gaskets either. Do it right the first time and you won't be sorry!
h dog |
I couldn't agree more, you thin out the tops of the pistons and you're inviting trouble. Trouble which usually occurs at the most inoportune time. I know guys that double up on head gaskets, but they're racing and expecting to yank her back down. I suspect that's not your goal.
Let us know what you do! greg |
Does anybody want to buy some trw pistons cheap? Looks like i'll be buying new pistons. Thanks for you help guys.. Terry
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Felpro makes a block saver that is used as a shim. They come .020 thick. If you're only out of the hole .015 then these would set you in .005 which is good. These are used with a standard Fel-Pro head gasket. I've seen them used on many drag motors and they work great.
Don |
Gotta side with Sizzler on this one. I would hate to read the thread where you trashed the rest of the motor trying to use the wrong pills.
Don't fight it, switch! |
Zero deck height with steel rods and a 0.040" head gasket is about a close as I would go.
Machining 0.015" off the ring land part of the piston is not going to affect piston reliability much if any on a N/A motor. As the piston has a dish I would bet that you are not actually reducing the crown thickness at all. On the other hand if you price having the pistons machined at a reputable shop I bet you'll find that a new set of pistons doesn't look so expensive after all. On the other hand machining the pistons is not a bad thing to do. I used to build 1430cc Mini Cooper S motors by taking Triumph 2.5PI pistons and machining more than 1/8" off the crown to make them work with Cooper S rods and an offset ground 1275 GT crank. Those suckers survived at 8000 rpm with no problems. |
I agree with Don. Some builder go as much as .010 positive piston above deck in racing engines for more quench.
.015 might be a pushing it, but a shim should work fine, and save time and money. If you are using heads that have not been milled, your chances look even better as far as valve/piston clearance. |
Ahhhh, we are now at that wonderful moment we qall hate in our hobby, decisions! You now have all the polar opinions and you're still .015 out. Now what? New pumps? Shim? Mill 'em off? Just like these beautiful cars we all love.... Your choice dude, let us know what you do!!!
Good luck.... |
May not be too bad
Check Corral.net. The mustang guys seem to like the '69 351, as the "strongest" ever cast. Several claim to be running with .015" over the deck. This flies in the face of popular wisdom, and all the books...but it seems to make horsepower.
Now, whether I would try this is another story. Good luck |
I stopped by the machine shop yesterday and they told me a price of 80 dollars to machine the tops. Mike is right on about the the piston. This is a dished piston and reduceing the ring land will only decrease the cup size and not affect the crown. The compression should go up a bit, but it was only 9 to 1 anyway. Also when I checked the piston to valve clearance with the heads on, I was at the minimun .08 on the intake side. To close for me so thought I'd have them flycut just a tad. 64 bucks for the flycut and 80 to cut the tops seems reasonable. Don i came real close to buying the shim but this seems like a better way to go. Thanks guys for your help. Terry
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This is an old thread, but did flipper0007 ever finish his engine?
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